Abstract [en]

Background:

Oral moist snuff (snus) is discussed as a safer alternative to smoking, and its use is increasing. Based on its documented effect on blood pressure, we hypothesized that use of snus increases the risk of heart failure.

Cox proportional hazards models were used to investigate possible associations of snus use with risk of a first hospitalization for heart failure.

Results:

In ULSAM, 95 men were hospitalized for heart failure, during a median follow up of 8.9 years. In a model adjusted for established risk factors including past and present smoking exposure, current snus use was associated with a higher risk of heart failure [hazard ratio (HR) 2.08, 95% confidence interval (CI) 1.03-4.22] relative to non-use. Snus use was particularly associated with risk of non-ischaemic heart failure (HR 2.55, 95% CI 1.12-5.82). In CWC, 545 men were hospitalized for heart failure, during a median follow up of 18 years. In multivariable-adjusted models, current snus use was moderately associated with a higher risk of heart failure (HR 1.28, 95% CI 1.00-1.64) and non-ischaemic heart failure (HR 1.28, 95% CI 0.97-1.68) relative to never tobacco use.

Conclusion:

Data from two independent cohorts suggest that use of snus may be associated with a higher risk of heart failure.

Abstract [en]

Previous investigations of snus use (oral moist snuff, a Swedish form of smokeless tobacco) and cardiovascular disease have generally focused on atherosclerotic events such as myocardial infarction and stroke, likely because smoking is such a well-established risk factor for atherosclerotic disease. Smokeless administration of tobacco circumvents most of the atherogenic effects of the combusted products from smoked tobacco, but it is possible that the potent autonomic and hemodynamic effects of snus and nicotine per se are detrimental for cardiovascular tissues.

The aim of this thesis was to investigate if snus is associated with development of heart failure and the prognosis after myocardial infarction. We used data from Swedish cohort studies and the national quality register for myocardial infarctions (SWEDEHEART), with linkages to national registers.

Snus use was associated with a higher risk of heart failure in a dose-response manner. This association was specific to non-ischemic heart failure, implying a direct myocardial effect, rather than an atherogenic effect (papers I and II).

Acute, short-term or long-term outcomes following a myocardial infarction were not consistently worse among snus users relative to snus non-users, although snus use was associated with an increased risk of death after myocardial infarction among never-smokers (paper III).

Discontinuation of snus use after a myocardial infarction was associated with an almost halved mortality risk, similar to the benefit associated with smoking cessation (paper IV).

Although smoking was consistently stronger related to all adverse outcomes, and with reservations due to the observational design, the findings from this thesis indicate that snus should not be regarded as harmless. Snus use was associated with a higher risk of heart failure and post-myocardial infarction mortality, which may have public health implications for the risk assessment of snus, and potentially other modes of smokeless nicotine.